Have you ever taken a photo where the colours appear all wrong? For instance with a strong blue or orange tint (what is called a colour cast)? If you ever took a picture at night, it most probably happened to you a fair few times. This is a case of wrong white balance: the colours are not well balanced with each other, and casts appear. One particularly visible consequence is that white is not pure white anymore, but slightly yellow or blue instead.

This is because not all light is created equal, and some have warmer components than others (i.e. they have stronger yellow and reds than blue and greens). We speak of light temperature, of which there is an actual scientific definition, though it's not worth getting into this now. For instance, tungsten light (the usual incandescent lamps) appears much warmer than daylight sun, which is why it appears so yellow on night photographs. Fluorescent lights, on the other hand, are quite cold, explaining the "sterile" and inhuman look some offices have.

Unless it is extremely basic, your camera probably has a White Balance setting (often abbreviated in WB). Its usual modes are Auto (abbreviated AWB), Sunny, Shade, Fluorescent and Tungsten (with standard icons). Choosing one other than Auto will tell the camera how to compensate for the current light conditions so that a white object really appears white.

Film photographers have it much harder, as the only two ways of controling white balance are to use a different film (some are known to be warmer than others) or to use coloured filters.

Despite its somewhat technical nature, white balance is a very important creative tool, as we tend to have instinctual reactions to the set of colours used in an image: warm tones convey an idea of comfort, softness, happiness, while cold colours are usually distant, hostile and cruel. If it fits your vision, you should not hesitate to introduce (subtle) colour casts to enhance the message you are trying to convey.

Choosing the right white balance may seem like a difficult task. After all, our brain is so good at compensating colour casts that we rarely notice if our current environment is more of a tungsten or a fluorescent light. There are however very good news for digital photographers: if you shoot raw instead of jpg (which we will discuss in more detail in a later lesson), you will be able to set white balance after the shoot, in post-processing, with no loss of image quality. In other words, you do not need to worry about white balance at all until you get back to your computer, at which point, as we will see in a moment, it is a much easier task.

If you want to get white balance right in camera (because you are shooting jpg, or because you want to spend as little time on the computer as possible), you have three possibilities:

You can trust the camera with the job and shoot in AWB. Most modern cameras will do a pretty good job as long as the conditions are reasonable, but all bets are off when you add mixed, complicated lighting. In short, you can probably forget about WB as long as you are shooting natural light by day, but you should be paying attention once you add any kind of artificial light.

You can try to guess what the light composition is and set the camera WB in the relevant mode. It helps to also know that "fluorescent" means the image will get warmer, while "tungsten" means it will get cooler - using the screen, you can use trial and error until you get a WB that corresponds to your vision. This is quite cumbersome and you will occasionally forget to reset your WB mode between shoots, but with enough practice, it can work well.

Finally, you can use a grey card to create your own WB mode. This is definitely the most accurate method, but it is also the most complex and time consuming. What you are doing is take a photo of a neutral gray piece of paper (anything will do, really, but many stores will be happy to sell you overpriced pieces of cardboard), then tell the camera that this should be its new reference point for WB from now on. Obviously, you will need to repeat this process every time the lighting changes.

If, on the other hand, you shoot raw, you can adjust WB in post. There are several ways to do this, one of which being to use the same modes than your camera or to use sliders to set light temperature to the exact values you want. However, the easiest method of all is simply to pick out a neutral part of the image and tell the software "this should be neutral, please adjust white balance accordingly". As long as you can find an object that should be some shade of grey, you obtain results just as accurate as if you had used the custom WB procedure. Of course, it will occasionally happen that you can't find anything neutral, and you might have to resort to the sliders and your own memory of the scene. To prevent this kind of scenarios, some photographers do take a picture of a grey card at the beginning of an important shoot, in order to have a point of reference.

Canon DSLRs are infamously poor at guessing the auto WB in tungsten lighting; I would assume the other manufacturers aren't much better. I used to try to set the WB in camera; quickly I gave up and now leave it on AWB all the time, to fix the colors later in PP.

Loveloveloveing this series. I know you'll run out of subjects eventually, but I don't want it to end. :-)

Although I almost always shoot in raw, I manually set my white balance to match the conditions that I'm shooting in. I've found that the presets on my Nikon work well 95% of the time (Tungsten, Fluorescent, Daylight, Shade, etc.) I've found that Auto White Balance will do screwy things sometimes.

When colors need to be 100% accurate, I would recommend using a store bought gray card, though. Yes, they are expensive, but you aren't paying for cardboard, you're paying for a specific, neutral shade of gray. Grabbing something that looks gray or white on location can result in you using a slightly warmer or cooler reference, and would defeat the purpose of using a gray card at all.

Typically, I shoot at least one reference photo that includes the gray card in the frame for each lighting condition (meaning that, if I were to change locations, time of day, or lighting setup, I would want a fresh gray card reference each time). In post production, use the gray part as the reference for white balance information. You can then apply the corrected white balance settings to all of the other photographs in the series.

The black and white portions of your card are more for exposure control than white balance. Because you have a true black and a true white reference, you can adjust your exposure (either in camera or in post production) to make sure that you maintain detail in both your shadows and highlights. I usually do that in camera by checking my histogram .

I know of a wedding photographer who uses a small target constantly during his wedding coverage. He has an assistant (or the subject) hold the target for the first photo, zooms in to almost fill the frame with the target, takes a shot, then checks his histogram for exposure. After that, he doesn't have to worry about a bride's white dress or the groom's black tux throwing off his in-camera meter and accidentally over or under exposing a frame. Later, in post, he uses the gray reference to insure that the colors are spot on.